Government lawyers defended Ontario's controversial ban on pit bulls from a constitutional challenge Tuesday by insisting the law is a vital tool in the province's efforts to protect the public from what they consider dangerous weapons.

Pit bulls have a "predilection to attack," Crown lawyer Michael Doi said as he described the broad-shouldered, snub-nosed animals as the dog preferred by criminals who want an extra level of security.

"In many ways, pit bulls are the automatic guns of the dog world," said Doi, as some spectators in the courtroom groaned in disagreement.

Doi described cases in which police were forced to shoot pit bulls dead because the dogs attacked officers trying to execute an arrest or search warrant at the home of a suspect.

"With the criminal element, the dog of choice is a pit bull."

The challenge is being argued by lawyer Clayton Ruby on behalf of Catherine Cochrane, who owns a two-year old pit bull mix. She is mounting the challenge with the support of animal-rights groups.

In court, the Crown described in graphic detail cases where children or adults were mauled by pit bulls in unprovoked attacks and suffered severe injuries that scarred them for life.

Superior Court Justice Thea Herman agreed that the attacks were vicious, but in cases where police had to shoot the dogs, their owners were the main problem, she noted.

She also acknowledged a point made in earlier arguments by Ruby that if pit bulls are banned, irresponsible owners and criminals would simply choose a different breed of dog.

"It raises the question: is the problem the dog or is the problem the owner?" she said.

Doi countered that the validity of the law is not in question — only whether it violates the Constitution.

"It's not the wisdom of the legislation that's at issue, it's the constitutionality of it," he said.

Just as there's no constitutional right to possess an automatic weapon, a banned weapon in Canada, "there is no constitutional right to own a pit bull."

The government has the right to take action against any threat to public safety, Doi noted.

Cochrane, who adopted Chess from the Toronto Humane Society as a puppy, said the ban has curtailed what she can do with her dog, who she says is friendly and not aggressive.

Documentation for the dog, whose bloodlines are unknown, classify it as a mastiff, a pit bull, or an American Staffordshire Terrier cross — one of the breeds covered by the ban.

As a result, Cochrane has to muzzle the dog and keep her on a leash at all times when out walking. Cochrane said she fears these limits will make her pet less friendly with other animals and people.

"I feel as though I'm being put in a position where I need to prove that I'm not guilty," Cochrane said. "To me, that's a reversal of how things work here."

On Monday, Ruby argued that the ban, put in place last August, is too broad because it encompasses several recognized breeds, along with any dog with "substantially similar" characteristics to those breeds.

The onus is on the owner to prove that the dog isn't a pit bull, he said.

If affected dogs aren't sterilized and muzzled and leashed while in public, the owner can face a fine of up to $10,000 or as much as six months in jail — or both.

Attaching a penalty of jail time to such a broad law is unconstitutional, said Ruby, who noted the law considers all pit bulls dangerous regardless of their actions and forces owners to take special measures as a result.

"I don't think it will prevent dog attacks," Cochrane said.

"Because it doesn't do anything to help people choose a dog that's right for them, or how to train a dog correctly, it just doesn't look at any roots of the problem."

Crown lawyer Zachary Green insisted the law is not vague or too broad, pointing to cases in Manitoba and Quebec where municipal pit bull bans similar to Ontario's have been upheld by appeal courts.

As long as the court is able to interpret the law, then it's not unconstitutionally vague, Green said.